The readme.txt file appears to be obsolete. However, the supplied file should work. I suggest that you compare your file to the one supplied and make the appropriate changes. Use a comparison program such as Meld, Winmerge, etc. and look for the changes with USPS comment tags.
You need to uninstall your old module before installing the new one. Failure to do so will result in leftover database entries, which then cause spurious unnamed entry fields like the ones in your image.
You can fix this by first uninstalling the current module. Then search through your database configuration table for any keys containing USPS and delete those. After that you can install the module again.